The present invention relates to a method for repairing an integrally bladed rotor for a turbine or turbo engine, in which a plurality of projecting vanes are arranged on the peripheral surface of the carrier, and to a method for manufacturing an integrally bladed rotor for a turbine or turbo engine, in which a plurality of projecting vanes are to be arranged on a peripheral surface of a carrier, each of which is welded to a stub, having a front face, projecting over the peripheral surface.
Such integrally bladed rotors can be manufactured by milling from the entire unit or by welding the individual vanes to the carrier. U.S. Pat. No. 4,883,216 describes a method of repairing and manufacturing such a rotor in which initially a collar is welded to the stubs projecting over the peripheral surface of the carrier around its entire periphery and subsequently a (replacement) vane is welded to this enlarged bonding surface, made up of stub and collar, which has a considerably widened bonding collar on the vane base. One disadvantage is that the vane cannot be welded in its final/finished form, and a very large amount of subsequent machining is required due to the two collars.
French Patent Application No. 22 26 241 describes a method for bonding vanes to a rotor carrier. The vanes include a projecting base having a supporting surface for transmitting joining forces. The vanes are welded to the rotor carrier using resistance welding.
One object of the present invention is to provide a method of repairing a rotor of a turbine or turbo engine in which the replacement vane section can be welded as far as possible in its finished form without many additional machining steps. It is another object of the present invention to provide a method of manufacturing such a rotor, in which the vanes can be welded to the carrier as far as possible in their finished form without many additional machining steps.
According one embodiment of the present invention, the repairing method includes the following steps: removing a vane section to be replaced leaving a stub section forming a first part of the vane, which has a front face for bonding to a replacement vane section; arranging an inductor around the front face of the stub section; positioning the replacement vane section, corresponding to the removed vane section in shape and size, on the stub section, one surface used as a joining surface of the replacement vane section and the front face of the stub section being essentially aligned with and opposite one another at a small distance; and welding the replacement vane section to the stub section in a protective gas atmosphere by exciting the inductor with high-frequency current and moving the replacement vane section and the stub section together, with the melted front face of the stub section and the surface of the replacement vane section in contact with one another.
One advantage of the repair method according to the present invention is that the induced high-frequency current is concentrated in the respective joining surfaces and these surfaces are only melted in the area near the surface, so that the replacement vane section and the stub section are pressed together using relatively little force and over an extremely short period of time. For this reason the replacement vane section can be easily held in the blade area.
Furthermore, particularly thin-walled, mechanically sensitive vanes can be replaced or attached in this way. It is also possible to join cast vanes to forged rotors (disks/rings) in manufacturing new units.
In one embodiment, the inductor is arranged at a greater distance from the joining surface in the vane front edge and rear edge areas than in the central area of the vane and the stub section, so the induced high-frequency electrical current heats the front face of the stub section and the surface of the replacement vane section as evenly as possible at all points, melting only the areas close to their respective surfaces.
The surface of the replacement vane section may be positioned at a distance of approximately 2 mm from the front face of the stub section prior to welding, so the front face of the stub section and the surface of the replacement vane section are evenly heated, melting only to a depth of approximately 0.1 mm.
The replacement vane section may be fitted into a plastic block in a non-slipping manner, so that the replacement vane section can be welded to the carrier in its final form without additional holding or supporting sections. In this manner, expensive machining steps no longer need to be performed on the replacement vane section.
The welding step may be performed in a maximum of 3 seconds, which guarantees an efficient process and ensures that the stub section and the replacement vane section melt in the areas of their respective surfaces. The replacement vane section and the stub section may be moved together a maximum of for example an additional 1 mm after contact of their surface and front face, so that any contaminants in the melt are pressed out at the sides, but the peripheral thickening of the joint is kept small.
In another embodiment, the vane blade section to be replaced, which is usually damaged, may be removed along a parting plane extending to the vane tip. In this manner, if only the vane tip area is damaged, only a small section of the vane has to be replaced, and not the entire vane.
The manufacturing method according to the present invention includes the following steps: arranging an inductor around the front face of the stub; positioning a vane on the stub, one surface of the vane and the front face of the stub being essentially aligned with and opposite one another at a small distance; and welding the vane to the stub in a protective gas atmosphere by exciting the inductor with high-frequency current and moving the vane and the stub together, with the melted front face of the stub and the surface of the vane in contact with one another.